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Author Topic:   water from foam
tbirdsey posted 05-06-2000 09:23 PM ET (US)   Profile for tbirdsey   Send Email to tbirdsey  
Have read many posts about the problem of water soaked foam - never thought it could happen to me, until yesterday. Thirty-six hours later, I think I have a solution - at least for small areas.

While adding some additional rollers to the trailer for my 19 Outrage with the boat on the trailer (yes it is possible), I noticed some areas on the keel where the gelcoat had been worn down to the glass. Another thing to fix before getting in the water this spring, I thought. Then I saw a drop of water appear in one of the spots and fall to the ground. My worst nightmare! After denial, depression, search for another explanation, etc I realized I had to find out how serious it was. A 1/4" drill into the spot where the drop was and two more about 1" on either side produced another drop. Probing with a wooden skewer kinda like testing a cake for doneness produced a wet skewer in two of the holes. A little more exploring seemed to indicate the problem was confined to a fairly small area right next to a roller and maybe some voids in the foam as well. Seems like the weight of the boat on the roller may have compressed the foam leading to some voids; that combined with the worn spot on the keel, boat in water, etc, etc...well, on to the solution. And I was NOT about to start carving out chunks of foam.

The exploratory holes did nothing to "drain" the foam; I assume the water is encapsulated in the foam and won't run out by itself, just like a sponge. It needed a push... or a pull. Well its hard to squeeze the hull so I thought about the pull concept and figured a vacuum might provide the "pull" and something primitive would be fairly easy to create using a plastic bag and a shop vac. Duct taped a freezer bag around the 1/4" holes, cut another hole and duct taped the smallest attachment I had for the shop vac, turned it on, and prayed! It works - sucks the water right out. Not a lot of water in my case, but definitely water.

I was fortunate to be dealing with a very small area maybe a few square inches of surface area on the hull by 3-4" deep. I don't see why this wouldn't work for larger areas just as well. I'm not sure how much the shop vac likes this although it didn't seem to overheat. Hopefully no more drops in the morning and I will fill the holes with foam and patch the fiberglass, gelcoat, etc. Anybody else ever try this??

jimh posted 05-07-2000 03:50 PM ET (US)     Profile for jimh  Send Email to jimh     
[about extracting water from foam with vacuum pump]

I haven't tried this--in fact I've never heard anyone propose it before--but it sounds like a good idea.

In the early building of FRG laminates, one technique was similar to this: the cloth layers are laid up between male/female molds and the resin drawn in and through the cloth using a vacuum pump.

Assuming the water in the foam is able to migrate--and it must or how else did it get from the inlet to where it is now--then a vacuum suction should be able to withdraw it back through the original inlet or one you've made closeby.

You might want to investigate a vacuum pump instead of burning out your ShopVac.


lhg posted 05-02-2001 12:22 AM ET (US)     Profile for lhg    
Keeping this information alive!
jameso posted 05-02-2001 09:55 AM ET (US)     Profile for jameso  Send Email to jameso     
I work for a small company that repairs aircraft components, some of them are composites and a lot of honeycomb material. To remove water we use vacum and heat. A vacum pump with a heat blanket for a couple of days and you should remove most of the water.
Since the foam in a whaler is supposed to be closed cell most water migration will be in areas where there are voids, small cracks in the gel coat will let water in that area. I just did a thermal image (IR) scan on a transom that had a cracked engine scupper,,,water had penetrated about 8 inches down in the area. Even though the foam is supposedly closed cell it is hydroscopic to some extent, because of this it may take hours or days for all the water to escape. Another note DO NOT heat area above 212 degrees F. When water turns to steam it expands 512 times! I have seen water in honeycomb components blow holes in aluminum skin.
Whalerdan posted 05-02-2001 12:03 PM ET (US)     Profile for Whalerdan  Send Email to Whalerdan     
I saw the guy on the Speed Vision show Ship Shape do this on a transom.

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